encryptpasswordrsa.cs

清华大学出版社出版的 移动应用开发宝典 张大威（2008）的附书源代码

using System;
using System.Text;
using System.Security.Cryptography;
using System.IO;
using System.Xml;

namespace Encryption
{
    class EncryptPasswordRSA
    {
        public void SavePassword(string cleartext)
        {
            RSACryptoServiceProvider rsaProvider = new RSACryptoServiceProvider();
            //Create a new instance of RSAParameters.
			RSAParameters RSAKeyInfo = new RSAParameters();

            RSAKeyInfo = ReadPublicKeyXML(RSAKeyInfo);

			//Import key parameters into RSA.
            rsaProvider.ImportParameters(RSAKeyInfo);

            //Encrypt the supplied data
            byte[] cipherText =
            rsaProvider.Encrypt(new UnicodeEncoding().GetBytes(cleartext), false);

            //Save the Cipher-Text
            using (System.IO.StreamWriter sw =
                new System.IO.StreamWriter(GetApplicationDirectory() + @"\UserKeyCipher.txt", false))
            {
                sw.Write(Convert.ToBase64String(cipherText));
                sw.Flush();
            }
        }

        private RSAParameters ReadPublicKeyXML(RSAParameters RSAKeyInfo)
        {
            // Read the public key from the XML file with a reader.
            using (Stream stm = File.OpenRead(GetApplicationDirectory() + @"\PublicKey.xml"))
            {
                XmlTextReader reader = new XmlTextReader(stm);
                // Do performant ref comparison
                string ev = reader.NameTable.Add("RSAKeyValue");
                while (reader.Read())
                {
                    if (reader.LocalName == ev)
                    {
                        // Process it!
                        int eventDepth = reader.Depth;
                        reader.Read();
                        while (reader.Depth > eventDepth)
                        {
                            if (reader.MoveToContent() == XmlNodeType.Element)
                            {
                                switch (reader.Name)
                                {
                                    case "Modulus":
                                        RSAKeyInfo.Modulus = Convert.FromBase64String(reader.ReadString());
                                        break;
                                    case "Exponent":
                                        RSAKeyInfo.Exponent = Convert.FromBase64String(reader.ReadString());
                                        break;
                                }
                            }
                            reader.Read();
                        }
                    }
                }
            }
            return RSAKeyInfo;
        }


        private string GetApplicationDirectory()
        {
          return System.IO.Path.GetDirectoryName(System.Reflection.Assembly.GetExecutingAssembly().GetModules()[0].FullyQualifiedName);
        }
    }    
}